1. Field of the Invention
The present invention relates to a method of fabricating a board having a periodically poled region, more in details, relates to a method of fabricating a board having a periodically poled region capable of fabricating a board having a periodically poled region without needing a complicated constitution for applying a pulse voltage or a complicated constitution for applying a strong electric field.
2. Description of the Related Art
In a related art, there is known a technology of providing a periodic domain inverting structure by forming a periodic electrode on a surface of a lithium niobate board (CLN board) having a congruent constitution, forming a plane electrode on a rear face thereof, and applying, for example, an electric field of 40 [kV/cm] and a pulse of a pulse width of 0.1 [second] to the electrodes two times (refer to, for example, Japanese Patent Publication No. 2969787 (7 column, 30 line through 8 column, 34 line) which is hereinafter referred as Patent Reference 1).
Further, there is known a technology of providing a periodically poled structure by forming a periodic electrode on a surface of a lithium niobate board (CLN board) or a lithium tantalate board (CLT board) having a congruent constitution, forming a plane electrode on a rear face thereof, and superposing a pulse voltage of a pulse width of 5 [μ second] and a direct current voltage to constitute a synthesized electric field of about 21 [kV/mm] so as to apply the synthesized electric field to these electrodes (refer to, for example, Japanese Patent Publication No. 3059080 ([0033] through [0047] [0060] [0066]) which is hereinafter referred as Patent Reference 2).
Further, there is known a technology of inverting polarization by forming a periodic electrode on a surface of a board comprising lithium tantalate near to a Ta excess or Li excess stoichiometric composition, forming a plane electrode on a rear face, and applying a pulse voltage of, for example, an electric field of several tens [kV/mm] in the case of the Ta excess board, or an electric field of about 0.5 through 4 [kV/mm] in the case of the Li excess board to these electrodes (refer to, for example, JP-A–2002-72266 ([0020] [0023] [0062] [0063] [0078] [0090]) which is hereinafter referred as Patent Reference 3).
It is necessary to apply a pulse voltage in any of the above–described related arts, and there poses a problem of needing a complicated constitution for applying the pulse voltage (power source or the like capable of outputting the pulse voltage of a short pulse width).
Further, although in [0040] through [0043] of Patent Reference 2, an example of applying only a direct current voltage is explained, a direct current electric field equal to or higher than about 20 [kV/mm] is applied and there poses a problem of needing a complicated constitution of applying a strong electric field (power source or the like capable of outputting a high voltage).